Free eBooks: The Best of SQL Server Central
SQL Server Central gives away the the best, most read and most popular articles in eBook format. The Best Of SQL Server Central Vol 1 and The Best Of SQL Server Central Vol 2 cover a lot of issues that SQL Server developers and admins should know like design, performance, administration and security. It also covers "myths" like the Count(*) vs Count(column name)
...many people believe COUNT (columnname) is faster than using COUNT (*), because COUNT (*) would have to read all columns of each row (just like executing a SELECT * FROM MYTABLE statement), while COUNT (columnname) only need to read the specified column. This is not true though, for several reasons…
The Best of SQL Server Central has a lot of screenshots and source code like any good reference.
Via [Gianluca's Blog]